1. Field of the Invention
The present invention relates to a tape carrier package and a liquid crystal display device including such a tape carrier package.
2. Description of the Related Art
FIG. 10 is a cross-sectional view showing the configuration of a conventional tape carrier package 1000 (hereinafter, referred to as "TCP") for driving a liquid crystal display panel 109.
A method for fabricating the conventional TCP 1000 shown in FIG. 10 is described below
First, a semiconductor chip 101 having gold bumps 105 is fabricated by plating electrodes (pads) which are formed on a wafer with gold so as to form gold bumps 105, attaching the resultant water with the bumps 105 onto a dicing sheet, and then dicing the wafer by dicing apparatus into the semiconductor chip 101 having a predetermined size.
Although the size and the height of each of the gold bumps 105 very depending on a bump pitch, the bump size and the bump height are typically within the range of about 40 to 100 .mu.m and within the range of about 10 to 20 .mu.m, respectively. In the case of a semiconductor chip for a liquid crystal device driver, the chip has typically an elongated shape with an aspect ratio (i.e., a ratio of length to width) in the range of about 10 to 20.
Then, the semiconductor chip 101 is placed into a device hole 107 of a tape carrier. The tape carrier includes an insulating film 102 made of polyimide or the like as a tape substrate, and a conductor pattern deposited thereon through an adhesive layer 103. The conductor pattern forms inner leads 108, output-side outer leads 114 serving as connection terminals for a liquid crystal device driving signal, and input-side outer leads 113 serving as source terminals for driving the semiconductor chip and as connection terminals for an image signal.
Next, in the inner lead bonding step, the gold bumps 105 on the semiconductor chip 101 and inner leads 108 of the tape carrier are bonded to each other by using an inner lead bonder. When the gold of the gold bumps 105 and tin of the inner leads 108 form an eutectic alloy, the bonding is completed. The inner leads 108 are formed by etching, for example, a copper foil. In order to form the autectic alloy, the surface of the inner lead 108 is plated with a tin layer having a thickness in the range of 0.1 to 0.3 .mu.m.
Since the semiconductor chip 101 is held by the inner leads 108 after the inner lead bonding step, a sealing liquid resin 106 is applied onto a predetermined area of the semiconductor chip 101 by a plotting method so as to plot the junction portion of the semiconductor chip 101 and the inner leads 108. Then, the liquid resin 106 is cured so as to coat the junction portion of the semiconductor chip 101 and the inner leads 108. The potting cure is carried out at about 100.degree. C. or higher for several hours. After the liquid resin 106 is cured, the resultant TCP 1000 is marked and is then subjected to a final test. Thereafter, the real-shaped TCP 1000 is shipped without performing a further process, or is cut into pieces to be shipped as slide carriers.
The TCP 1000 fabricated by the steps as described above has the structure which is the most advantageous for packaging a semiconductor device having multi-connection terminals into a compact size. Thus, at present, such TCPs are the most widely utilized as carrier packages for a semiconductor device for driving a liquid crystal display panel.
As shown in FIG. 10, the TCP 1000 is preattached to connection terminals provided in the outer peripheral region of the liquid crystal display panel 109 with an anisotropic conductor film 110. Then, the output-side outer lead 114 is aligned with the corresponding connection terminals provided in the outer peripheral region of the liquid crystal display panel 109. The aligned portion is subjected to thermo-compressive bonding using a heated tool so as to attach the TCP 1000 and the liquid crystal display panel 109 to each other. The input-side outer leads 113 are connected to a printed wiring board 111.
In this case, the TCP 1000, excluding a connecting portion of the output-side outer leads 114 within the liquid crystal display panel 109, protrudes from an edge 109a of the liquid crystal display panel 109. When an amount of the protruding portion form the edge 109a of the liquid crystal display panel 109 (hereinafter, referred to as "frame size") is large, the overall liquid crystal module size also becomes large. Therefore, a ratio of an area of a display screen to a module area is decreased. However, the frame size should be minimized, in particular, in the case where the TCP is utilized in equipment having a strict limitation in a module outer shape, for example, in a notebook-sized or subnotebook-sized personal computer or a personal digital assistance (PDA).
In order to reduce the frame size so as to satisfy the needs of market for such personal computers is or personal digital assistances, the following TCPs shown in FIGS. 11 to 14 have been proposed.
FIG. 11 is a cross-sectional view showing the configuration of a TCP 1100 having a bent structure for driving a liquid crystal display panel, attached to the liquid crystal display panel 109. In the TCP 1100 having a bent structure, the portion protruding from the edge 109a of the liquid crystal display panel 109 is bent toward the bottom face of the liquid crystal display panel 109. An insulating resin 112 is applied on the corners formed by the bending. The insulation resin 112 has an anti-bending resistance and protects the conductor pattern 104 which is exposed through slits formed in the insulating film 102 at the corners.
By thus bending the protruding portion toward the bottom side of the liquid crystal display panel 109, an apparent frame size is reduced as shown in FIG. 11. However, an additional portion for bending should be provided for the TCP 1100, the size of the TCP 1100 itself is increased. Accordingly, the fabrication cost thereof is disadvantageously increased. Moreover, since the TCP 1100 is incorporated into a liquid crystal module in a bent state, a thickness of the liquid crystal module is disadvantageously increased.
FIG. 12 is a cross-sectional view showing a conventional TCP 1200 utilizing a slim-type semiconductor chip 101a for driving a liquid crystal display panel, attached to the liquid crystal display panel. The slim-type semiconductor chip 101a utilized in the TCP 1200 shown in FIG. 12 has a bar-like shape rather then a rectangular shape as conventional.
As shown in FIG. 12, the frame size of the slim type TCP 1200 is increased as compared with the bent type TCP 1100, Nevertheless, since the size of the TCP 1200 itself is reduced, the slim-type TCP is advantageous in view of cost. Moreover, since it is not necessary to bend the protruding region, the fabrication process can be simplified as compared with the bent type TCP 1100 as shown in FIG. 11,
On the other hand, as described above, the bent type TCP 1100 is disadvantageous in terms of cost compared with the slim-type TCP 1200. Therefore, the bent type TCP 1200 is not suitable for application to a large liquid crystal display panel employing a large number of TCPs.
In this manner, various type TCPs are mounted onto liquid crystal display panels, taking advantage of features of the respective structures. Among these, in order to satisfy the conflicting needs of the market, that is, the enlargement of a display region of a liquid crystal display panel and the reduction of size of a liquid crystal module, the slim type TCP 1200 having a reduced chip size has been employed so as to reduce the frame size.
However, the reduction of the chip size in a slim type TCP is now reaching the limits due to an increase in the number of output-side outer leads of a semiconductor chip and incorporation of additional new circuits and new features required for a semiconductor chips.
There has been proposed another configuration of the TCP referred to as "inside pad type" so as to reduce the frame size. FIG. 13 shows a TCP 1300 utilizing an inside pad type semiconductor chip 101b for driving a liquid crystal display panel. In such a configuration, for example, the electrode bumps 116 of the semiconductor chip 101b are positioned so as to be offset toward the central portion from the edge portion of the semiconductor chip 101b.
As shown in FIG. 13, the TCP 1300 includes spacer holding members 115 for holding a predetermined distance between the semiconductor chip 101b and the insulating film 102. In the TCP 1300, a sealing resin 106 is provided so as to coat a joining portion of the inner leads 108 and the semiconductor chip 101b and joining portions of the input-side and output-side outer leads 113 and 114 and the semiconductor chip 101b. The sealing resin 106 covers over the width of the semiconductor chip 101b.
The frame size is the total of a length of the inner-side outer lead 114 between the edge 109a of the liquid crystal display panel 109 and one edge of the semiconductor chip 101b the size (width) of the semiconductor chip 101b including TCP wiring region therein, and a size of the semiconductor chip 101b, a length of the outer-side outer lead 113 between the other edge of the semiconductor chip 101b and an edge 111a of the printed wiring board 111, and additional width of the printed wiring board 111.
The total width of the TCP 1300 can be defined as a width of the semiconductor chip 101b plus an input-side wiring portion 133a and an output-side wiring portion 133b, where the input-sides and output-side wiring portions 133a and 133b are portions of the TCP 1300 extending from the width of the semiconductor chip 101b towards signal input side and signal output side, respectively.
That is, the frame size cannot be reduced to be less than the minimum overall size of the inside pad type TCP 1300 other than the connecting portion of the output-side outer leads 114 overlapping with the peripheral region of the liquid crystal display panel 109.
Alternatively, instead of utilizing a TCP, a liquid crystal module utilizing bare chip mount having a chip on glass (COG) structure has been employed to reduce the frame size of the liquid crystal module. FIG. 14 is a partial cross-sectional view showing a conventional liquid crystal module 1400 utilizing a COG structure for driving a liquid crystal display panel. As shown in FIG. 14, the liquid crystal module 1400 includes a liquid crystal display panel 119 having an upper glass substrate 119a, a lower glass substrate 119b, and a pair of polarizers 124, a back light 120, a glass epoxy substrate 121, a semiconductor chip 101c having bumps 122 for COG, and a flexible substrate 123. Since the semiconductor chip 101c can be mounted onto wirings (not shown) formed on the lower glass substrate 119b without assembling into a TCP, it is considered that the cost can be reduced.
In the case of the COG shown in FIG. 14, a wafer test is carried out when the wafer is fabricated. However, there are some steps after the wafer test such as dicing the wafer to obtain semiconductor chips and putting the semiconductor chips, which have been determined as nondefective in the wafer test, onto a tray, before the semiconductor chips are mounted on a liquid crystal display module. Thus, there is a possibility that the semiconductor chips which have been judged as nondefective in the wafer test become defective in the subsequent steps due to change in electrical characteristics thereof or adhesion of foreign material or dust thereon through these fabrication steps.
Moreover, the COG method is a bare chip mounting. Therefore, the surface of the semiconductor chip 101c may be contaminated or damaged on the surface in a handling step before the mounting step of the semiconductor chip 101c.
In addition, the COG is disadvantageous in that a burn-in test or the like cannot be performed, compared with TCPs for which a burn-in test is performed in a relatively simple manner. For TCPs, therefor, initial defects occurring therein after mounting can be relatively easily eliminated before delivered into the market. However, there is a possibility that an initial defect occurs in the market.
Furthermore, in the case where a defective semiconductor chip is mounted, the defective semiconductor chip should be removed and replaced with a nondefective chip. However, for COG, great effort must be made to repair the bare semiconductor chip which has already been mounted.
The COG method still has disadvantages as follows: In utilizing the COG method, an arrangement of the electrode bumps 122 on the COG type semiconductor chip 101c is determined in accordance with a substrate, such as the lower glass substrate 119b as shown in FIG. 14 or a glass epoxy substrate, on which the semiconductor chip 101c is mounted. Therefore, in the case where the chip size is changed in accordance with the version-up or the requirement for a reduced chip size, it is necessary to rearrange the electrode bumps 122 on the semiconductor chip 101c. Once the bump electrode arrangement of the semiconductor chip 101c is changed, the design of the bonded portion of the substrate on which the semiconductor chip 101c is mounted should be also changed in accordance with a new bump arrangement of the semiconductor chip 101c. The design of the substrate should be changed each time when a size of the semiconductor chip 101c is changed, resulting in an increase of cost.
On the other hand, a change in the substrate on which the semiconductor chip 101c is mounted and the resulting change in a bonding portion thereof for the semiconductor chip 101c require a change in the arrangement of electrode bumps 122 of the semiconductor chip 101c.
Accordingly, in the case where the semiconductor chip 101a or the substrate on which the semiconductor chip 101c is to be mounted is changed, the COG method does not have much flexibility and tolerance for the change.